In the above referenced commonly assigned U.S. Pat. No. 4,962,316, entitled "Frequency Domain Integrating Resonant Superconducting Transmission Line Detector" Michael D. Jack discloses a FIRST detector that is comprised of a folded superconducting transmission line coupled at an input port to a narrow band microwave source and coupled at an output port to a microwave power monitor. An optically induced change in an inductance of the transmission line shifts the transmission line phase velocity and resonant frequency. This shift in resonant frequency attenuates the propagating wave amplitude proportionally to the product of the Q and the frequency shift. The FIRST detector is disclosed as a three layer structure having a bottom ground plane electrode and a top, superconducting radiation absorbing electrode. Interposed between the top and bottom electrodes is a dielectric layer. The FIRST detector is fabricated as a folded transmission line and is operated within a frequency range from several hundreds of KHz (10.sup.3 Hz) to one thousand GHz (10.sup.9 Hz). The device provides a realization of an optical detection dynamic range of eight orders of magnitude.
It is thus one object of the invention to provide another embodiment of a FIRST detector constructed as a five layer device wherein the superconducting folded transmission line electrode is interposed between a top and a bottom RF ground plane electrode and is insulated therefrom by adjacent dielectric layers, and wherein radiation that is detected is absorbed within the top, superconducting, RF ground plane electrode.
Advanced IR sensors that are required to operate in an ionizing radiation environment are typically further required to generate high rate, multiple samples per dwell. Such sensors generally also require complex spatial/temporal signal processing algorithms to discriminate against sample data that is corrupted due to gamma radiation or Compton electron events. Unfortunately, these demanding requirements may adversely impact signal processing rates, power consumption and the I/O capability of the sensor by as much as an order of magnitude over those sensors designed for operation in a more benign environment.
It is thus another object of the invention to provide apparatus enabling low power and compact focal plane sensors, based on superconductive detectors, to operate in an ionizing radiation environment with minimal gamma discrimination processing.
It is a further object of the invention to eliminate current or proposed focal plane gamma discrimination algorithms and electronics by utilizing the gamma discrimination provided by a pair of stacked FIRST detectors.